The 4.5ft-long young dolphin was discovered at Weymouth’s Bowleaze Cove on Sunday, leading to a probe led by the Natural History Museum’s Cetacean Strandings Investigation Programme (CSIP).
The CSIP said it could carry out a post-mortem examination to determine the likely cause of death because the animal was still “very fresh”.
According to the Dorset Wildlife Trust, which reported the incident to the CSIP, the carcass was collected for examination on Monday.
The trust’s Sarah Hodgson said: “There are many reasons why these animals die.
“It could be as a result of human activity, such as by-catch from fisheries, entanglement in ghost-fishing gear or pollution – or it could just be from natural causes.”
Luke Webb, who was visiting Dorset from Wiltshire, spotted the male, short-beaked common dolphin while walking along the beach with his family.
He said: “There were a couple of people trying to help it back into the sea – I think they thought it was just stranded and still alive but it wasn’t.
“It was really sad.”
He said there were no signs of decomposition or markings on the mammal.
Local Neal Buckoke, who came across the animal lying on the shore, told the Daily Echo it looked almost as though it were still alive.
He said: “It was awful to see – just heartbreaking really.
“It was very small, and could have been either a porpoise or a dolphin. But either way, there were no marks on it to suggest how it died. It could have ingested poison or plastic – it could be anything.
“You do see it a lot with whales that wash up in Baltic countries; when their deaths are investigated, scientists discover their stomachs are full of plastic – to the extent that they literally cannot eat.”
The animal was found close to a stream that runs over the beach and into the sea, which also serves as a sewage outflow during heavy rainfall.
This, Mr Buckoke said, made him think “it must be pollution”.
He added: “Either that, or it could be something to do with the two big trawlers that were off the coast for ages. But there weren’t any net marks visible.”
It follows the death of a striped dolphin, a species rarely seen in the country’s waters, at Kent’s Isle of Thanet last month.
Usually found in deep tropical to warm temperate oceanic waters, they are known for their distinct pattern, which includes thin stripes that run from the eye to the flipper.
As the British Divers Marine Life Rescue found the 1.7m juvenile female striped dolphin at Minnis Bay, they said: “This is the first recorded stranding of this species in Kent since 1996.
“Striped dolphins are usually found in warmer waters, generally preferring deep water and are usually seen in pods of around 25 or above. The cause of death is unknown.
“Thanet Council are working with the Natural History Museum and Cetacean Stranding Investigation Programme to try and recover the body for further investigation.”
If you find a live-stranded cetacean, please contact British Divers Marine Life Rescue (01825 765546 – 24 hours) urgently to engage a rescue. Never try to return it to the sea.
If you find a dead-stranded animal in Dorset, inform Dorset Wildlife Trust by calling 01305 264620 (Monday-Friday, 9am-5pm) or emailing [email protected] You can also call CSIP on 0800 652 0333.